1. Field of the Invention
This present invention relates to an optical system which is capable of enhancing a specific polarization state of a light beam and a light source system including the same.
2. Description of the Prior Art
The demand for various types of display devices has increased in the past decade. For instance, the most popular at this stage is the LCD display device and projector. These display machines use polarized light beam propagating through the components within them to achieve desired functions. Therefore, how to get a specific polarized light efficiently has been an important topic. Instead of using a conventional polarizer to absorb the unwanted polarized component from an unpolarized light, a polarization conversion device can be utilized to recycle the unwanted polarization component to increase the efficiency of display and projector. A previously proposed way to convert the non-polarized light beams of a light source into linearly polarized light beams having a single polarization state, was taught in, for example, U.S. Pat. No. 5,122,895 (Polarization Converter for converting Randomly Polarized Light to Linearly Polarized Light). In this patent, a so-called PS converter is disclosed. The P-polarized light component refers to the electric field oscillation of P light component being parallel to the plane of the incident light beam. The S-polarized light component refers to the electric field oscillation of S light component being vertical to the plane of the incident light beam.
Typically, in a system of LCD display or projector, the conventional polarization plate (polarizer) absorbs the unwanted polarized light component within the incident light beam, to obtain the required polarized light beam. The maximum output efficiency for the conventional polarizer is about 50%. In addition to lacking of efficiency as to the conventional approaches, the configuration of conventional PS converters is complex and typically involves relatively high costs of production. In addition, the display apparatus which implements the polarization state converter consumes more power than expected.
To meet the needs which cure the drawbacks mentioned above, the present invention intends to provide a novel solution of optical system capable of enhancing a specific polarization state of a light beam. By this invention, a thin film approach is used to implement a simple anisotropic film system which induces a strong polarization conversion. Together with a polarization beam splitter, other than boosting to a higher conversion efficiency, the requirements for enhancing one polarization state from an unpolarized light can be met easily.